List of some Physics Websites
http://www.colorado.edu/physics/2000/index.pl A great physics site
http://phet.colorado.edu/index.php This is from the same university. Highly recommended website. It has excellent applets suitable for classrooms
http://www.fearofphysics.com Good for students as well as teachers
http://www.aapt.org/ American Association of Physics teachers
http://physics.nist.gov/cuu/Units/ Units / Uncertainties
http://www.psrc-online.org/ Physical Sciences Resource Centre
http://www.ieee-virtual-museum.org/index.php Electrical Engineering
http://www.walter-fendt.de/ph14e/ Java applets Really good
http://www.npl.uiuc.edu/~a-nathan/pob/ Physics of baseball
http://www.physlink.com/index.cfm Astronomy links
http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html Good for facts and definitions. Some very useful explanations
http://www.howstuffworks.com/ A very good website especially for the application of physics
http://www.educypedia.be/education/physicsexperiments.htm
good experiments and demonstrations not only in physics but in other sciences too. Some links are broken
http://www.channel4learning.net/apps/homeworkhigh/ Designed to help students with HW
http://www.practicalphysics.org A very good site with a lot of demonstrations and experiment ideas
http://www.s-cool.co.uk/default.asp A revision site mainly for A level
http://www.physics.org has many physics sites with possibility of asking questions getting news updates and lists of physics careers
http://www.vuw.ac.nz/scps-demos An excellent site with a lot of physics demonstrations and experiments with videos and lists of equipment

General science

http://www.bbc.co.uk/sn/
http://www.squashedfrogs.co.uk/
http://www.kungfuscience.org/
http://www.metoffice.gov.uk/education/
http://education.jlab.org/
http://www.factmonster.com/science.html
http://www.sciencenewsforkids.org/
http://www.teachers.tv/
http://www.topmarks.co.uk/
http://www.iop.org/activity/education/index.html